diff -r 48c4eec2b7e6 -r 8c2e4d02f4ef wp/wp-includes/blocks/cover/block.json
--- a/wp/wp-includes/blocks/cover/block.json	Fri Sep 05 18:40:08 2025 +0200
+++ b/wp/wp-includes/blocks/cover/block.json	Fri Sep 05 18:52:52 2025 +0200
@@ -78,6 +78,9 @@
 		"tagName": {
 			"type": "string",
 			"default": "div"
+		},
+		"sizeSlug": {
+			"type": "string"
 		}
 	},
 	"usesContext": [ "postId", "postType" ],